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Equity - Summary of Capital Stock (Detail)
shares in Millions, $ in Millions, $ in Millions
Dec. 31, 2020
TWD ($)
shares
Dec. 31, 2020
USD ($)
shares
Dec. 31, 2019
TWD ($)
shares
Disclosure of classes of share capital [abstract]      
Authorized shares 28,050.0 28,050.0 28,050.0
Authorized capital | $ $ 280,500.0   $ 280,500.0
Issued and paid shares 25,930.3 25,930.3 25,930.3
Issued capital $ 259,303.8 $ 9,234.5 $ 259,303.8